Added assignment 6 directory and worksheet

29 files changed, 2011 insertions, 0 deletions

diff --git a/dev/a6-harold/.gitignore b/dev/a6-harold/.gitignore
new file mode 100644
index 0000000..dd1a9a8
--- /dev/null
+++ b/dev/a6-harold/.gitignore
@@ -0,0 +1,2 @@
+config.h
+build
diff --git a/dev/a6-harold/CMakeLists.txt b/dev/a6-harold/CMakeLists.txt
new file mode 100644
index 0000000..83ca82d
--- /dev/null
+++ b/dev/a6-harold/CMakeLists.txt
@@ -0,0 +1,209 @@
+# Original Author(s) of this File: 
+#   Daniel Keefe, 2017, University of Minnesota
+#  
+# Author(s) of Significant Updates/Modifications to the File:
+#   ... 
+
+
+
+# You are encouraged to copy this example, move it outside of the MinGfx directory, and use
+# it as a starting point for your project.  When you do this, you'll have to edit the
+# following line as needed to point to the MinGfx install prefix used on your system.
+
+# !!!!!!!!!!!!! EDIT THE FOLLOWING LINE AS NEEDED !!!!!!!!!!!!! 
+list(APPEND CMAKE_PREFIX_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../build/install ../..)
+
+
+
+#### BASIC PROJECT SETUP ####
+
+project(a6-harold)
+
+# Using 3.9 to get a modern version of FindOpenGL.cmake
+cmake_minimum_required (VERSION 3.9) 
+
+# Dependencies that are auto-downloaded, built, and installed for you will go in the 
+# directory pointed to by the CMAKE_INSTALL_PREFIX.  It defaults to a location inside
+# the build directory.
+if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT OR "${CMAKE_INSTALL_PREFIX}" STREQUAL "")
+    set (CMAKE_INSTALL_PREFIX "${CMAKE_BINARY_DIR}/install" CACHE PATH "default install path" FORCE )
+endif()
+
+# Add to paths cmake uses to search for scripts, modules, and config packages
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake ${CMAKE_INSTALL_PREFIX})
+list(INSERT CMAKE_PREFIX_PATH 0 ${CMAKE_INSTALL_PREFIX})
+
+include(MessageMacros)
+h1("Building ${PROJECT_NAME}")
+h2("Configuring paths")
+
+message(STATUS "Module path: ${CMAKE_MODULE_PATH}")
+message(STATUS "Prefix path: ${CMAKE_PREFIX_PATH}")
+message(STATUS "Install prefix: ${CMAKE_INSTALL_PREFIX}")
+
+set(DATA_DIR_BUILD ${CMAKE_CURRENT_SOURCE_DIR}/data)
+set(DATA_DIR_INSTALL ${CMAKE_INSTALL_PREFIX}/share/${PROJECT_NAME}/data)
+
+message(STATUS "Data dir (in build tree): ${DATA_DIR_BUILD}")
+message(STATUS "Data dir (in install tree): ${DATA_DIR_INSTALL}")
+
+set(SHADERS_DIR_BUILD ${CMAKE_CURRENT_SOURCE_DIR}/shaders)
+set(SHADERS_DIR_INSTALL ${CMAKE_INSTALL_PREFIX}/share/${PROJECT_NAME}/shaders)
+
+message(STATUS "Shaders dir (in build tree): ${SHADERS_DIR_BUILD}")
+message(STATUS "Shaders dir (in install tree): ${SHADERS_DIR_INSTALL}")
+
+
+# Configure a header file to pass some of the CMake settings to the source code
+configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
+    ${CMAKE_CURRENT_SOURCE_DIR}/config.h
+)
+
+#### SOURCE FOR THIS PROJECT ####
+h2("Configuring source files")
+
+set(SOURCEFILES
+    billboards.cc
+    harold_app.cc
+    edge_mesh.cc
+    ground.cc
+    main.cc
+    sky.cc
+)
+
+set(HEADERFILES
+    billboards.h
+    harold_app.h
+    config.h
+    edge_mesh.h
+    ground.h
+    sky.h
+)
+
+set(EXTRAFILES
+    config.h.in
+    README.md
+)
+
+set(SHADERFILES
+    shaders/artsy.vert
+    shaders/artsy.frag
+    shaders/outline.vert
+    shaders/outline.frag
+    shaders/stroke2d.vert
+    shaders/stroke2d.frag
+    shaders/stroke3d.vert
+    shaders/stroke3d.frag
+)
+
+set_source_files_properties(${EXTRAFILES} PROPERTIES HEADER_FILE_ONLY TRUE)
+set_source_files_properties(${SHADERFILES} PROPERTIES HEADER_FILE_ONLY TRUE)
+
+source_group("Shaders" FILES ${SHADERFILES})
+
+
+#### COMPILE OPTIONS ####
+
+h2("Configuring Compiler Options")
+
+
+
+message(STATUS "Building for " ${CMAKE_SYSTEM_NAME} ".")
+
+# Linux specific
+if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+  add_definitions(-DLINUX)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
+endif()
+
+
+# Apple specific
+if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+  add_definitions(-DOSX)
+
+  # RPATH settings, see https://cmake.org/Wiki/CMake_RPATH_handling
+  set(CMAKE_MACOSX_RPATH ON)
+
+  # use, i.e. don't skip the full RPATH for the build tree
+  SET(CMAKE_SKIP_BUILD_RPATH  FALSE)
+
+  # when building, don't use the install RPATH already
+  # (but later on when installing)
+  SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE) 
+
+  SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
+
+  # add the automatically determined parts of the RPATH
+  # which point to directories outside the build tree to the install RPATH
+  SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+
+  # the RPATH to be used when installing, but only if it's not a system directory
+  LIST(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/lib" isSystemDir)
+  IF("${isSystemDir}" STREQUAL "-1")
+     SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
+  ENDIF("${isSystemDir}" STREQUAL "-1")
+
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
+endif()
+
+
+# Windows specific
+if (WIN32)
+  add_definitions(-DWIN32)
+
+  if(NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+    message(FATAL_ERROR
+        "You must use the 64 bit version of the compiler. Be sure to set the correct generator when configuring through CMake.")
+  endif()
+endif()
+
+
+
+
+#### DEFINE TARGET(S) ####
+
+h2("Defining Target(s)")
+
+add_executable(${PROJECT_NAME} ${SOURCEFILES} ${HEADERFILES} ${EXTRAFILES} ${SHADERFILES})
+
+
+
+#### FIND AND ADD DEPENDENCIES ####
+
+h2("Adding Dependencies")
+set(EXTERNAL_DIR external)
+
+
+# MinGfx (linked with an imported cmake target so no need to specify include dirs)
+# This will try to find MinGfxConfig.cmake, which should have been installed under
+# CMAKE_INSTALL_PREFIX/lib/cmake/MinGfx when you installed the MinGfx Toolkit.
+find_package(MinGfx REQUIRED)
+target_link_libraries(${PROJECT_NAME} PUBLIC MinGfx::MinGfx)
+
+
+# Add dependency on OpenGL
+include(UseOpenGL)
+UseOpenGL(${PROJECT_NAME} PUBLIC ${EXTERNAL_DIR})
+
+
+
+#### INSTALL TARGET(S) ####
+
+h2("Configuring Install Target")
+
+# The install locations are relative to the CMAKE_INSTALL_PREFIX variable
+install(TARGETS ${PROJECT_NAME} RUNTIME DESTINATION bin)
+
+install(
+    DIRECTORY data/
+    DESTINATION ${DATA_DIR_INSTALL}
+    OPTIONAL
+)
+
+install(
+    DIRECTORY shaders/
+    DESTINATION ${SHADERS_DIR_INSTALL}
+    OPTIONAL
+)
diff --git a/dev/a6-harold/README.md b/dev/a6-harold/README.md
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/dev/a6-harold/README.md
diff --git a/dev/a6-harold/billboards.cc b/dev/a6-harold/billboards.cc
new file mode 100644
index 0000000..5ec508a
--- /dev/null
+++ b/dev/a6-harold/billboards.cc
@@ -0,0 +1,206 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "billboards.h"
+
+Billboards::Billboards() {
+    
+}
+
+
+Billboards::~Billboards() {
+    
+}
+
+
+void Billboards::Init(ShaderProgram *stroke3d_shaderprog) {
+    stroke3d_shaderprog_ = stroke3d_shaderprog;
+}
+
+
+/// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+/// device coordinates) to a 3D point on a plane defined by an "origin", which can
+/// really be any point coincident with the plane, and the plane normal.  Returns
+/// true if the screen point projects onto the plane and stores the result in
+/// plane_point.  Returns false if the screen point does not project onto the plane.
+bool Billboards::ScreenPtHitsPlane(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                                 const Point3 &plane_origin, const Vector3 &plane_normal,
+                                 const Point2 &normalized_screen_pt, Point3 *plane_point)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    Point3 pt3d = GfxMath::ScreenToNearPlane(view_matrix, proj_matrix, normalized_screen_pt);
+    Ray ray(eye, (pt3d - eye).ToUnit());
+    float t;
+    return ray.IntersectPlane(plane_origin, plane_normal, &t, plane_point);
+}
+
+
+/// Checks to see if a ray starting at the eye point and passing through 2D
+/// normalized screen point projects onto any of the billboards in the scene. If
+/// so, returns the id of the closest billboard intersected.  If not, returns -1.
+int Billboards::IntersectBillboard(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                                   const Point2 &normalized_screen_pt)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    int id = -1;
+    float best_i_time = -1.0;
+    
+    Point3 pt3d = GfxMath::ScreenToNearPlane(view_matrix, proj_matrix, normalized_screen_pt);
+    Ray ray(eye, (pt3d - eye).ToUnit());
+    
+    Point3 i_point;
+    float i_time;
+    int i_tri_id;
+    for (int i=0; i<billboards_.size(); i++) {
+        Matrix4 to_billboard_space = billboards_[i].transform.Inverse();
+        Ray ray_billboard_space = to_billboard_space * ray;
+        if ((ray_billboard_space.IntersectAABB(billboards_[i].bounding_box, &i_time)) &&
+            (ray_billboard_space.IntersectMesh(billboards_[i].mesh, &i_time, &i_point, &i_tri_id)) &&
+            ((best_i_time == -1.0) || (i_time < best_i_time))) {
+            id = i;
+        }
+    }
+    
+    return id;
+}
+
+
+/// Adds a new stroke as a billboard by projecting it onto a plane parallel
+/// to the filmplane that intersects with the base point, which should lie
+/// on the ground.
+void Billboards::AddBillboardStroke(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                                    const std::vector<Point2> &stroke2d, const Mesh &stroke2d_mesh,
+                                    const Color &stroke_color, Ground *ground_ptr)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    // Create a new billboard
+    Billboard b;
+    b.color = stroke_color;
+    b.transform = Matrix4();
+    b.mesh = stroke2d_mesh;
+    
+    // find the base point for the billboard
+    ground_ptr->ScreenPtHitsGround(view_matrix, proj_matrix, stroke2d[0], &b.anchor_pt);
+    Vector3 norm = (eye - b.anchor_pt);
+    norm[1] = 0.0;    // with 0 change in Y so the billboard does not tilt
+    norm.Normalize(); // convert to a unit vector
+    
+    // project the stroke into 3D to lie on the projection plane
+    std::vector<Point3> verts;
+    for (int i=0; i<b.mesh.num_vertices(); i++) {
+        Point2 pscreen = Point2(b.mesh.read_vertex_data(i)[0], b.mesh.read_vertex_data(i)[1]);
+        Point3 pplane;
+        ScreenPtHitsPlane(view_matrix, proj_matrix, b.anchor_pt, norm, pscreen, &pplane);
+        verts.push_back(pplane);
+    }
+    
+    Matrix4 to_canonical_billboard = Matrix4::Align(b.anchor_pt, Vector3::UnitY(), norm,
+                                                    Point3::Origin(), Vector3::UnitY(), Vector3::UnitZ());
+    
+    for (int i=0; i<verts.size(); i++) {
+        verts[i] = to_canonical_billboard * verts[i];
+    }
+    
+    b.mesh.SetVertices(verts);
+    
+    for (int i=0; i<b.mesh.num_vertices(); i++) {
+        b.bounding_box = b.bounding_box + AABB(b.mesh.read_vertex_data(i));
+    }
+    b.bounding_box.set_user_data((int)billboards_.size());
+    
+    billboards_.push_back(b);
+}
+
+
+/// Edits an existing billboard by adding an additional stroke to it.
+void Billboards::AddToBillboard(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                                int billboard_id, const Mesh &stroke2d_mesh,
+                                const Color &stroke_color)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    // Really what this does is add a new billboard that lies in the same plane
+    // as the one we are "editing" and has the same anchor point so that they
+    // will both rotate the same way.
+    Billboard b;
+    b.color = stroke_color;
+    b.transform = Matrix4();
+    b.mesh = stroke2d_mesh;
+    
+    b.anchor_pt = billboards_[billboard_id].anchor_pt;
+    
+    
+    Vector3 norm = (eye - b.anchor_pt);
+    norm[1] = 0.0;    // with 0 change in Y so the billboard does not tilt
+    norm.Normalize(); // convert to a unit vector
+    
+    // project the stroke into 3D to lie on the projection plane
+    std::vector<Point3> verts;
+    for (int i=0; i<b.mesh.num_vertices(); i++) {
+        Point2 pscreen = Point2(b.mesh.read_vertex_data(i)[0], b.mesh.read_vertex_data(i)[1]);
+        Point3 pplane;
+        ScreenPtHitsPlane(view_matrix, proj_matrix, b.anchor_pt, norm, pscreen, &pplane);
+        verts.push_back(pplane);
+    }
+    
+    Matrix4 to_canonical_billboard = Matrix4::Align(b.anchor_pt, Vector3::UnitY(), norm,
+                                                    Point3::Origin(), Vector3::UnitY(), Vector3::UnitZ());
+    
+    for (int i=0; i<verts.size(); i++) {
+        verts[i] = to_canonical_billboard * verts[i];
+    }
+    
+    b.mesh.SetVertices(verts);
+    
+    for (int i=0; i<b.mesh.num_vertices(); i++) {
+        b.bounding_box = b.bounding_box + AABB(b.mesh.read_vertex_data(i));
+    }
+    b.bounding_box.set_user_data((int)billboards_.size());
+    
+    billboards_.push_back(b);
+}
+
+
+void Billboards::UpdateBillboardRotations(const Point3 &current_eye_point) {
+    // Whenver the camera moves, we also need to rotate the billboards so
+    // that they always face the viewer.
+    for (int i=0; i<billboards_.size(); i++) {
+        // billboards are stored in a coordinate system where the base is
+        // at (0,0,0), rotation happens about the Y axis, and the billboard's
+        // normal is +Z.
+        Point3 a_p = Point3(0,0,0);        // 'anchor point' in billboard coordinates
+        Vector3 a_v1 = Vector3::UnitY();   // 'up' in billboard coordinates
+        Vector3 a_v2 = Vector3::UnitZ();   // 'normal' in billboard coordinates
+        
+        Point3 b_p = billboards_[i].anchor_pt;    // 'anchor point' in world coordinates
+        Vector3 b_v1 = Vector3::UnitY();          // 'up' in world coordinates
+        Vector3 b_v2 = (current_eye_point - b_p); // 'normal' in world coordinates
+        b_v2[1] = 0.0;    // force 0 change in Y so the billboard does not tilt
+        b_v2.Normalize(); // convert to a unit vector
+        
+        billboards_[i].transform = Matrix4::Align(a_p,a_v1,a_v2, b_p,b_v1,b_v2);
+    }
+}
+
+
+void Billboards::Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix) {
+    // Draw billboard meshes
+    stroke3d_shaderprog_->UseProgram();
+    stroke3d_shaderprog_->SetUniform("projectionMatrix", proj_matrix);
+    for (int i=0; i<billboards_.size(); i++) {
+        Matrix4 model_matrix = billboards_[i].transform;
+        Matrix4 modelview_matrix = view_matrix * model_matrix;
+        stroke3d_shaderprog_->SetUniform("modelViewMatrix", modelview_matrix);
+        stroke3d_shaderprog_->SetUniform("strokeColor", billboards_[i].color);
+        billboards_[i].mesh.Draw();
+    }
+    stroke3d_shaderprog_->StopProgram();
+}
+
diff --git a/dev/a6-harold/billboards.h b/dev/a6-harold/billboards.h
new file mode 100644
index 0000000..7de2799
--- /dev/null
+++ b/dev/a6-harold/billboards.h
@@ -0,0 +1,78 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#ifndef BILLBOARDS_H_
+#define BILLBOARDS_H_
+
+#include <mingfx.h>
+using namespace mingfx;
+
+#include "ground.h"
+
+/** Billboards are strokes planted in the ground that rotate automatically to
+ face the viewer.  This class holds the entire collection of billboard strokes.
+ */
+class Billboards {
+public:
+    Billboards();
+    virtual ~Billboards();
+    
+    void Init(ShaderProgram *stroke3d_shaderprog);
+    
+    /// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+    /// device coordinates) to a 3D point on a plane defined by an "origin", which can
+    /// really be any point coincident with the plane, and the plane normal.  Returns
+    /// true if the screen point projects onto the plane and stores the result in
+    /// plane_point.  Returns false if the screen point does not project onto the plane.
+    bool ScreenPtHitsPlane(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                         const Point3 &plane_origin, const Vector3 &plane_normal,
+                         const Point2 &normalized_screen_pt, Point3 *plane_point);
+    
+    
+    /// Checks to see if a ray starting at the eye point and passing through 2D
+    /// normalized screen point projects onto any of the billboards in the scene. If
+    /// so, returns the id of the closest billboard intersected.  If not, returns -1.
+    int IntersectBillboard(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                           const Point2 &normalized_screen_pt);
+    
+    
+    /// Adds a new stroke as a billboard by projecting it onto a plane parallel
+    /// to the filmplane that intersects with the anchor point, which should lie
+    /// on the ground.
+    void AddBillboardStroke(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                            const std::vector<Point2> &stroke2d, const Mesh &stroke2d_mesh,
+                            const Color &stroke_color, Ground *ground_ptr);
+    
+    /// Edits an existing billboard by adding an additional stroke to it.
+    void AddToBillboard(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                        int billboard_id, const Mesh &stroke2d_mesh,
+                        const Color &stroke_color);
+    
+    
+    /// Adjusts the transformation matrix used to draw each billboard so that the
+    /// billboard will face the camera.  Needs to be called each time the camera
+    /// is moved within the scene.
+    void UpdateBillboardRotations(const Point3 &current_eye_point);
+    
+    
+    /// Draws all of the billboards
+    void Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix);
+    
+private:
+
+    // each billboard stores the following
+    struct Billboard {
+        Mesh mesh;
+        Color color;
+        Point3 anchor_pt;
+        AABB bounding_box;
+        Matrix4 transform;
+    };
+
+    // the array of all active billboards
+    std::vector<Billboard> billboards_;
+    
+    ShaderProgram *stroke3d_shaderprog_;
+};
+
+#endif
diff --git a/dev/a6-harold/cmake/DownloadHelper.txt.in b/dev/a6-harold/cmake/DownloadHelper.txt.in
new file mode 100644
index 0000000..fb29bff
--- /dev/null
+++ b/dev/a6-harold/cmake/DownloadHelper.txt.in
@@ -0,0 +1,26 @@
+# This file is part of the MinGfx cmake build system.  
+# See the main MinGfx/CMakeLists.txt file for authors, copyright, and license info.
+
+# This is a "helper" cmake project -- the only thing this project does is download
+# the external project.  So, the configure, build, install, and test commands for 
+# ExternalProject_Add() are intentionally set as NOPs.  
+
+cmake_minimum_required (VERSION 3.9) 
+
+project(@EXT_PROJECT_NAME@-download)
+
+include(ExternalProject)
+ExternalProject_Add(
+  @EXT_PROJECT_NAME@
+  SOURCE_DIR "@DOWNLOAD_DIR@/@EXT_PROJECT_NAME@/src"
+  BINARY_DIR "@DOWNLOAD_DIR@/@EXT_PROJECT_NAME@/download-helper"
+  @DOWNLOAD_OPTIONS@
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND ""
+  INSTALL_COMMAND ""
+  TEST_COMMAND ""
+  LOG_DOWNLOAD ON
+  GIT_PROGRESS 1
+)
+
+
diff --git a/dev/a6-harold/cmake/ExternalProjectDownloadBuildInstall.cmake b/dev/a6-harold/cmake/ExternalProjectDownloadBuildInstall.cmake
new file mode 100644
index 0000000..ce12d1d
--- /dev/null
+++ b/dev/a6-harold/cmake/ExternalProjectDownloadBuildInstall.cmake
@@ -0,0 +1,98 @@
+# This file is part of the MinGfx cmake build system.  
+# See the main MinGfx/CMakeLists.txt file for authors, copyright, and license info.
+
+
+# Calling CMAKE_CURRENT_LIST_DIR inside a function returns the list dir of the calling script
+# but we want the list dir of this file in order to find the DownloadHelper.txt.in file, which
+# should be stored right next to this one.  So, defining this variable outside the scope of the
+# functions below.
+set(DIR_OF_THIS_FILE ${CMAKE_CURRENT_LIST_DIR})  
+
+
+
+# Usage:  
+# ExternalProject_Download(
+#     # This first argument is the name of the project to download.  It is required:
+#     glm
+#
+#     # Additional arguments specify how to download the project using GIT, SVN, CVS, or URL.
+#     # These can be any of the arguments used for the downloading step of the cmake builtin
+#     # ExternalProject_Add command. 
+#     GIT_REPOSITORY "https://github.com/g-truc/glm.git"
+#     GIT_TAG master
+#     etc..
+# )
+function(ExternalProject_Download EXT_PROJECT_NAME DOWNLOAD_DIR)
+
+    include(MessageMacros)
+    h1("BEGIN EXTERNAL PROJECT DOWNLOAD (${EXT_PROJECT_NAME}).")
+
+    h2("Creating a download helper project for ${EXT_PROJECT_NAME}.")
+
+    set(DOWNLOAD_OPTIONS ${ARGN})
+    string (REGEX REPLACE "(^|[^\\\\]);" "\\1 " DOWNLOAD_OPTIONS "${DOWNLOAD_OPTIONS}")
+
+
+    file(MAKE_DIRECTORY ${DOWNLOAD_DIR}/${EXT_PROJECT_NAME})
+    configure_file(
+        ${DIR_OF_THIS_FILE}/DownloadHelper.txt.in 
+        ${DOWNLOAD_DIR}/${EXT_PROJECT_NAME}/download-helper/CMakeLists.txt
+    )
+
+    h2("Generating build files for the ${EXT_PROJECT_NAME} download helper project.")
+    execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" . WORKING_DIRECTORY "${DOWNLOAD_DIR}/${EXT_PROJECT_NAME}/download-helper")
+
+    h2("Building the ${EXT_PROJECT_NAME} download helper project.  (This actually performs the download and may take some time...)")
+    execute_process(COMMAND "${CMAKE_COMMAND}" --build . WORKING_DIRECTORY "${DOWNLOAD_DIR}/${EXT_PROJECT_NAME}/download-helper")
+
+    h2("Completed download of external project ${EXT_PROJECT_NAME}.")
+
+endfunction()
+
+
+# Usage:  
+# ExternalProject_BuildAndInstallNow(
+#     # This first argument is the name of the external project to download.  It is required:
+#     VRPN
+#     # This second argument is the relative path from ${EXTERNAL_DIR_NAME}/projectname/ to the project's
+#     # main CMakeLists.txt file:
+#     src
+#
+#     # Additional arguments are passed on as options to the cmake build file generator
+#     -DVRPN_BUILD_DIRECTSHOW_VIDEO_SERVER=OFF
+#     -DVRPN_BUILD_HID_GUI=OFF
+#     etc..
+# )
+function(ExternalProject_BuildAndInstallNow EXT_PROJECT_NAME DOWNLOAD_DIR RELPATH_TO_CMAKELISTS)
+
+    include(MessageMacros)
+    h1("BEGIN EXTERNAL PROJECT BUILD AND INSTALL (${EXT_PROJECT_NAME}).")
+
+    # any extra args to the function are interpreted as arguments for the cmake config process
+    set(CMAKE_CONFIG_OPTIONS ${ARGN})
+
+    # always set the install prefix to be the same as for the main project
+    list(APPEND CMAKE_CONFIG_OPTIONS -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX})
+
+    #string (REGEX REPLACE "(^|[^\\\\]);" "\\1 " CMAKE_CONFIG_OPTIONS "${CMAKE_CONFIG_OPTIONS}")
+
+
+    set(SRC_DIR "${DOWNLOAD_DIR}/${EXT_PROJECT_NAME}/${RELPATH_TO_CMAKELISTS}")
+    set(BUILD_DIR "${CMAKE_BINARY_DIR}/external/${EXT_PROJECT_NAME}")
+
+    file(MAKE_DIRECTORY ${BUILD_DIR})
+
+    h2("Generating build files for external project ${EXT_PROJECT_NAME}.")
+    message(STATUS "Using source dir: ${SRC_DIR}")
+    message(STATUS "Using build dir: ${BUILD_DIR}")
+    message(STATUS "Config options: ${CMAKE_CONFIG_OPTIONS}")
+
+    execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" ${SRC_DIR} ${CMAKE_CONFIG_OPTIONS} WORKING_DIRECTORY ${BUILD_DIR})
+
+    h2("Building external project ${EXT_PROJECT_NAME}.  (This may take some time...)")
+    execute_process(COMMAND "${CMAKE_COMMAND}" --build ${BUILD_DIR} --target install)
+
+    h2("Completed external build of ${EXT_PROJECT_NAME}.")
+
+endfunction()
+
diff --git a/dev/a6-harold/cmake/MessageMacros.cmake b/dev/a6-harold/cmake/MessageMacros.cmake
new file mode 100644
index 0000000..4628e5c
--- /dev/null
+++ b/dev/a6-harold/cmake/MessageMacros.cmake
@@ -0,0 +1,17 @@
+# This file is part of the MinVR cmake build system.  
+# See the main MinVR/CMakeLists.txt file for authors, copyright, and license info.
+
+
+macro(h1 TITLE)
+  string(TOUPPER ${TITLE} TITLE)
+  message(STATUS "\n\n==== ${TITLE} ====")
+endmacro()
+
+macro(h2 TITLE)
+  message(STATUS "\n* ${TITLE}")
+endmacro()
+
+macro(h3 TITLE)
+  message(STATUS "- ${TITLE}")
+endmacro()
+
diff --git a/dev/a6-harold/cmake/UseOpenGL.cmake b/dev/a6-harold/cmake/UseOpenGL.cmake
new file mode 100644
index 0000000..2ec5ffb
--- /dev/null
+++ b/dev/a6-harold/cmake/UseOpenGL.cmake
@@ -0,0 +1,52 @@
+# This file is part of the MinGfx cmake build system.  
+# See the main MinGfx/CMakeLists.txt file for authors, copyright, and license info.
+
+# Either finds a pre-installed version or complains.
+
+# Usage: In your CMakeLists.txt, somewhere after you define the target that depends
+# on the OpenGL library (typical with something like add_executable(${PROJECT_NAME} ...) 
+# or add_library(${PROJECT_NAME} ...)), add the following two lines:
+
+#    include(UseOpenGL)
+#    UseOpenGL(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/external)
+
+# The second argument can be either PUBLIC, PRIVATE, or INTERFACE, following the keyword
+# usage described here: 
+# https://cmake.org/cmake/help/latest/command/target_include_directories.html
+
+# The third argument is the directory to use for downloading the external project if
+# autobuild is used.
+
+
+
+macro(UseOpenGL YOUR_TARGET INTERFACE_PUBLIC_OR_PRIVATE DOWNLOAD_DIR)
+
+    message(STATUS "Searching for OpenGL...")
+
+	# Check to see if the library is already installed on the system    
+    # CMake ships with FindOpenGL.cmake and in CMake 3.9+ it defines
+    # the imported targets OpenGL::GL and OpenGL::GLU.  Using these is
+    # now the preferred way to link with OpenGL and all of its dependencies.
+	# See https://cmake.org/cmake/help/v3.9/module/FindOpenGL.html
+	find_package(OpenGL)
+
+	if (NOT ${OPENGL_FOUND})
+	    message(FATAL_ERROR "OpenGL was not found on the system.  MinGfx can auto-download and build many dependencies for you, but not OpenGL. It should come pre-installed on your system.")
+	endif()
+
+    message(STATUS "Ok: OpenGL Found.")
+    message(STATUS "OpenGL headers: ${OPENGL_INCLUDE_DIR}")
+    message(STATUS "OpenGL libs: ${OPENGL_LIBRARIES}")
+
+
+    message(STATUS "Linking target ${YOUR_TARGET} with ${INTERFACE_PUBLIC_OR_PRIVATE} dependency OpenGL::GL.")
+    target_link_libraries(${YOUR_TARGET} ${INTERFACE_PUBLIC_OR_PRIVATE} OpenGL::GL)
+
+    if (${OPENGL_GLU_FOUND})
+        message(STATUS "Linking target ${YOUR_TARGET} with ${INTERFACE_PUBLIC_OR_PRIVATE} dependency OpenGL::GLU.")
+        target_link_libraries(${YOUR_TARGET} ${INTERFACE_PUBLIC_OR_PRIVATE} OpenGL::GLU)
+    endif()
+
+	target_compile_definitions(${YOUR_TARGET} ${INTERFACE_PUBLIC_OR_PRIVATE} -DUSE_OPENGL)
+
+endmacro()
diff --git a/dev/a6-harold/config.h.in b/dev/a6-harold/config.h.in
new file mode 100644
index 0000000..9798f4c
--- /dev/null
+++ b/dev/a6-harold/config.h.in
@@ -0,0 +1,15 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+
+// The file config.h.in is processed by cmake to produce config.h.  This
+// replaces strings of the form "at"CMAKE_VARIABLE_NAME"at" with the value
+// of the corresponding cmake variable, allowing us to pass directory paths
+// and other information configured with cmake into our C++ code.
+
+
+#define DATA_DIR_BUILD "@DATA_DIR_BUILD@"
+#define DATA_DIR_INSTALL "@DATA_DIR_INSTALL@"
+
+#define SHADERS_DIR_BUILD "@SHADERS_DIR_BUILD@"
+#define SHADERS_DIR_INSTALL "@SHADERS_DIR_INSTALL@"
diff --git a/dev/a6-harold/data/toonDiffuse.png b/dev/a6-harold/data/toonDiffuse.png
new file mode 100644
index 0000000..d2e40d9
--- /dev/null
+++ b/dev/a6-harold/data/toonDiffuse.png
diff --git a/dev/a6-harold/data/toonSpecular.png b/dev/a6-harold/data/toonSpecular.png
new file mode 100644
index 0000000..c13a32f
--- /dev/null
+++ b/dev/a6-harold/data/toonSpecular.png
diff --git a/dev/a6-harold/edge_mesh.cc b/dev/a6-harold/edge_mesh.cc
new file mode 100644
index 0000000..1abe2e0
--- /dev/null
+++ b/dev/a6-harold/edge_mesh.cc
@@ -0,0 +1,235 @@
+/** CSci-4611 Assignment 5:  Art Render
+ */
+
+#include "edge_mesh.h"
+
+EdgeMesh::EdgeMesh() : gpuDirty_(true) {
+    
+}
+
+EdgeMesh::~EdgeMesh() {
+}
+
+
+
+void EdgeMesh::CreateFromMesh(const Mesh &mesh) {
+    verts_.clear();
+    norms_.clear();
+    indices_.clear();
+    leftNorms_.clear();
+    rightNorms_.clear();
+    
+    // temp data holders for use while constructing the mesh in an indexed primitives mode
+    std::vector<Point3> vertices;                   // vertex positions
+    std::vector<Vector3> normals;                   // vertex normals
+    std::vector<Vector3> leftNormals, rightNormals; // normals of adj. faces
+    std::vector< std::vector<unsigned int> > triangles;      // fin triangles
+
+    for (int t = 0; t < mesh.num_triangles(); t++) {
+        std::vector<unsigned int> tri = mesh.read_triangle_indices_data(t);
+        Point3 a = mesh.read_vertex_data(tri[0]);
+        Point3 b = mesh.read_vertex_data(tri[1]);
+        Point3 c = mesh.read_vertex_data(tri[2]);
+        Vector3 e1 = b-a;
+        e1.Normalize();
+        Vector3 e2 = c-a;
+        e2.Normalize();
+        Vector3 n = e1.Cross(e2);
+        
+        //Vector3 n = ((b-a).cross(c-a)).to_unit();
+        //std::cout << n << std::endl;
+        addEdge(&vertices, &normals, &leftNormals, &rightNormals, &triangles, mesh, tri[0], tri[1], n);
+        addEdge(&vertices, &normals, &leftNormals, &rightNormals, &triangles, mesh, tri[1], tri[2], n);
+        addEdge(&vertices, &normals, &leftNormals, &rightNormals, &triangles, mesh, tri[2], tri[0], n);
+    }
+    
+    // now transfer data to the member variable data holders
+    for (int i=0; i<vertices.size(); i++) {
+        verts_.push_back(vertices[i][0]);
+        verts_.push_back(vertices[i][1]);
+        verts_.push_back(vertices[i][2]);
+        norms_.push_back(normals[i][0]);
+        norms_.push_back(normals[i][1]);
+        norms_.push_back(normals[i][2]);
+        leftNorms_.push_back(leftNormals[i][0]);
+        leftNorms_.push_back(leftNormals[i][1]);
+        leftNorms_.push_back(leftNormals[i][2]);
+        rightNorms_.push_back(rightNormals[i][0]);
+        rightNorms_.push_back(rightNormals[i][1]);
+        rightNorms_.push_back(rightNormals[i][2]);
+    }
+    
+    for (int i=0; i<triangles.size(); i++) {
+        indices_.push_back(triangles[i][0]);
+        indices_.push_back(triangles[i][1]);
+        indices_.push_back(triangles[i][2]);
+    }
+    gpuDirty_ = true;
+}
+
+
+void EdgeMesh::addEdge(std::vector<Point3> *vertices,
+                       std::vector<Vector3> *normals,
+                       std::vector<Vector3> *leftNormals,
+                       std::vector<Vector3> *rightNormals,
+                       std::vector< std::vector<unsigned int> > *triangles,
+                       const Mesh &mesh, int v0, int v1, Vector3 n)
+{
+    // edgeMap contains the index of the first of four consecutive vertices
+    // that form the quad fin
+
+    EdgeMap::iterator it = edgeMap.find(std::make_pair(v1, v0));
+    if (it != edgeMap.end()) { // found
+        int v = it->second;
+        (*rightNormals)[v+0]
+            = (*rightNormals)[v+1]
+            = (*rightNormals)[v+2]
+            = (*rightNormals)[v+3]
+            = n;
+    }
+    else {
+        int v = (int)vertices->size();
+        edgeMap[std::make_pair(v0, v1)] = v;
+        
+        vertices->push_back(mesh.read_vertex_data(v0));
+        vertices->push_back(mesh.read_vertex_data(v0));
+        vertices->push_back(mesh.read_vertex_data(v1));
+        vertices->push_back(mesh.read_vertex_data(v1));
+        
+        normals->push_back(Vector3());
+        normals->push_back(mesh.read_normal_data(v0));
+        normals->push_back(Vector3());
+        normals->push_back(mesh.read_normal_data(v1));
+        
+        leftNormals->push_back(n);
+        leftNormals->push_back(n);
+        leftNormals->push_back(n);
+        leftNormals->push_back(n);
+        
+        rightNormals->push_back(-n);
+        rightNormals->push_back(-n);
+        rightNormals->push_back(-n);
+        rightNormals->push_back(-n);
+
+        std::vector<unsigned int> tri1;
+        tri1.push_back(v+0);
+        tri1.push_back(v+2);
+        tri1.push_back(v+3);
+        triangles->push_back(tri1);
+        
+        std::vector<unsigned int> tri2;
+        tri2.push_back(v+0);
+        tri2.push_back(v+3);
+        tri2.push_back(v+1);
+        triangles->push_back(tri2);
+    }
+}
+
+
+
+void EdgeMesh::UpdateGPUMemory() {
+    if (gpuDirty_) {
+        // sanity check -- for each attribute that is added make sure the number
+        // of triangles is equal to the number of tris in the verts array.
+        if (norms_.size() / 3 != num_vertices()) {
+            std::cerr << "EdgeMesh::UpdateGPUMemory() -- warning: the number of per vertex normals in the mesh is not equal to the number vertices in the mesh. (N = " << norms_.size() / 3 << ", V = " << num_vertices() << ")" << std::endl;
+        }
+        if (leftNorms_.size() / 3 != num_vertices()) {
+            std::cerr << "EdgeMesh::UpdateGPUMemory() -- warning: the number of per vertex left-normals in the mesh is not equal to the number vertices in the mesh. (LN = " << leftNorms_.size() / 3 << ", V = " << num_vertices() << ")" << std::endl;
+        }
+        if (rightNorms_.size() / 3 != num_vertices()) {
+            std::cerr << "EdgeMesh::UpdateGPUMemory() -- warning: the number of per vertex right-normals in the mesh is not equal to the number vertices in the mesh. (RN = " << rightNorms_.size() / 3 << ", V = " << num_vertices() << ")" << std::endl;
+        }
+        
+        GLsizeiptr totalMemSize = 0;
+        
+        GLsizeiptr vertsMemSize = verts_.size() * sizeof(float);
+        GLsizeiptr vertsMemOffset = 0;
+        totalMemSize += vertsMemSize;
+        
+        GLsizeiptr normsMemSize = norms_.size() * sizeof(float);
+        GLsizeiptr normsMemOffset = totalMemSize;
+        totalMemSize += normsMemSize;
+        
+        GLsizeiptr leftNormsMemSize = leftNorms_.size() * sizeof(float);
+        GLsizeiptr leftNormsMemOffset = totalMemSize;
+        totalMemSize += leftNormsMemSize;
+
+        GLsizeiptr rightNormsMemSize = rightNorms_.size() * sizeof(float);
+        GLsizeiptr rightNormsMemOffset = totalMemSize;
+        totalMemSize += rightNormsMemSize;
+
+        glGenBuffers(1, &vertexBuffer_);
+        glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer_);
+        glBufferData(GL_ARRAY_BUFFER, totalMemSize, NULL, GL_STATIC_DRAW);
+        
+        glBufferSubData(GL_ARRAY_BUFFER, vertsMemOffset, vertsMemSize, &verts_[0]);
+        glBufferSubData(GL_ARRAY_BUFFER, normsMemOffset, normsMemSize, &norms_[0]);
+        glBufferSubData(GL_ARRAY_BUFFER, leftNormsMemOffset, leftNormsMemSize, &leftNorms_[0]);
+        glBufferSubData(GL_ARRAY_BUFFER, rightNormsMemOffset, rightNormsMemSize, &rightNorms_[0]);
+        
+        glGenVertexArrays(1, &vertexArray_);
+        glBindVertexArray(vertexArray_);
+        glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer_);
+        
+        // attribute 0 = vertices (required)
+        int attribID = 0;
+        int nComponents = 3;
+        glEnableVertexAttribArray(attribID);
+        glVertexAttribPointer(attribID, nComponents, GL_FLOAT, GL_FALSE, nComponents*sizeof(GLfloat), (char*)0 + vertsMemOffset);
+        
+        // attribute 1 = normals (required)
+        attribID = 1;
+        nComponents = 3;
+        glEnableVertexAttribArray(attribID);
+        glVertexAttribPointer(attribID, nComponents, GL_FLOAT, GL_TRUE, nComponents*sizeof(GLfloat), (char*)0 + normsMemOffset);
+
+        // attribute 2 = left normals (required)
+        attribID = 2;
+        nComponents = 3;
+        glEnableVertexAttribArray(attribID);
+        glVertexAttribPointer(attribID, nComponents, GL_FLOAT, GL_TRUE, nComponents*sizeof(GLfloat), (char*)0 + leftNormsMemOffset);
+
+        // attribute 3 = right normals (required)
+        attribID = 3;
+        nComponents = 3;
+        glEnableVertexAttribArray(attribID);
+        glVertexAttribPointer(attribID, nComponents, GL_FLOAT, GL_TRUE, nComponents*sizeof(GLfloat), (char*)0 + rightNormsMemOffset);
+        
+        glBindVertexArray(0);
+        
+        
+        glGenBuffers(1, &elementBuffer_);
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer_);
+        glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices_.size() * sizeof(unsigned int), &indices_[0], GL_STATIC_DRAW);
+        
+        
+        gpuDirty_ = false;
+    }
+}
+
+
+void EdgeMesh::Draw() {
+    if (gpuDirty_) {
+        UpdateGPUMemory();
+    }
+    
+    // set defaults to pass to shaders any for optional attribs
+    glVertexAttrib3f(1, 0.0, 0.0, 1.0);      // normal = +Z
+    glVertexAttrib3f(2, 0.0, 0.0, 1.0);      // left-normal = +Z
+    glVertexAttrib3f(3, 0.0, 0.0, 1.0);      // right-normal = +Z
+    
+    glBindVertexArray(vertexArray_);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer_);
+    glDrawElements(GL_TRIANGLES, (GLsizei)indices_.size(), GL_UNSIGNED_INT, (void*)0);
+    glBindVertexArray(0);
+}
+
+
+int EdgeMesh::num_vertices() const {
+    return (int)verts_.size()/3;
+}
+
+int EdgeMesh::num_triangles() const {
+    return (int)indices_.size()/3;
+}
diff --git a/dev/a6-harold/edge_mesh.h b/dev/a6-harold/edge_mesh.h
new file mode 100644
index 0000000..5120d0b
--- /dev/null
+++ b/dev/a6-harold/edge_mesh.h
@@ -0,0 +1,82 @@
+/** CSci-4611 Assignment 5:  Art Render
+ */
+
+#ifndef EDGE_MESH_H
+#define EDGE_MESH_H
+
+#include <mingfx.h>
+using namespace mingfx;
+
+#include <vector>
+
+
+/** This special kind of mesh stores two triangles that form a quadralateral
+ along each edge of an existing mesh.  The quad initially has a width=0, but
+ when rendered, two of the vertices are extended along the surfaces normal
+ direction, which creates a "fin" that can be drawn as a thick border.  This
+ can be used to create a silhouette edge renderer if the shader only extends
+ the edges that lie along a silhouette of the mesh.
+ */
+class EdgeMesh {
+public:
+    EdgeMesh();
+    virtual ~EdgeMesh();
+
+    /// Creates two triangles along each edge of the mesh passed in.
+    void CreateFromMesh(const Mesh &mesh);
+
+    /// Saves the mesh data to the GPU - must be called with InitOpenGL or Draw.
+    void UpdateGPUMemory();
+    
+    /// Num vertices in the edge mesh
+    int num_vertices() const;
+    
+    /// Num triangles in the edge mesh
+    int num_triangles() const;
+    
+    /// Access to vertex position by vertex number
+    Point3 vertex(int vertexID) const;
+
+    /// Access to vertex normal by vertex number
+    Vector3 normal(int vertexID) const;
+
+    /// Access to vertex color by vertex number
+    Color color(int vertexID) const;
+
+    /// Access to vertex texture coords by vertex number
+    Point2 tex_coords(int textureUnit, int vertexID) const;
+    
+
+    /// Draws the mesh assuming a shader has already been bound.
+    void Draw();
+    
+private:
+    
+    // Some routines and variables are needed internally to construct the edge
+    // mesh from a regular mesh.
+    
+    typedef std::map<std::pair<int,int>,int> EdgeMap;
+    EdgeMap edgeMap;
+
+    void addEdge(std::vector<Point3> *vertices,
+                 std::vector<Vector3> *normals,
+                 std::vector<Vector3> *leftNormals,
+                 std::vector<Vector3> *rightNormals,
+                 std::vector< std::vector<unsigned int> > *triangles,
+                 const Mesh &mesh, int v0, int v1, Vector3 n);
+
+    std::vector<float> verts_;          // vertex positions
+    std::vector<float> norms_;          // normals
+    std::vector<unsigned int> indices_; // indices
+    std::vector<float> leftNorms_;      // normals of adjacent triangles
+    std::vector<float> rightNorms_;
+
+    GLuint vertexBuffer_;
+    GLuint vertexArray_;
+    GLuint elementBuffer_;
+
+    bool gpuDirty_;
+};
+
+#endif
+
diff --git a/dev/a6-harold/ground.cc b/dev/a6-harold/ground.cc
new file mode 100644
index 0000000..51d4d92
--- /dev/null
+++ b/dev/a6-harold/ground.cc
@@ -0,0 +1,283 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "ground.h"
+
+
+Ground::Ground() : diffuse_ramp_(GL_CLAMP_TO_EDGE),
+    specular_ramp_(GL_CLAMP_TO_EDGE), light_pos_(30,30,30)
+{
+    
+}
+
+Ground::~Ground() {
+    
+}
+
+Mesh* Ground::mesh_ptr() { return &ground_mesh_; }
+
+
+void Ground::Init(const std::vector<std::string> &search_path) {
+    // init ground geometry, a simple grid is used.  if it is running too slow,
+    // you can turn down the resolution by decreasing nx and ny, but this will
+    // make the hills look more jaggy.
+    const int nx = 150;
+    const int ny = 150;
+    const float size = 100.0;
+    std::vector<Point3> verts;
+    std::vector<Vector3> norms;
+    for (int j = 0; j <= ny; j++) {
+        for (int i = 0; i <= nx; i++) {
+            float x = size*(float)j/nx - size/2.0f;
+            float y = size*(float)i/ny - size/2.0f;
+            verts.push_back(Point3(x, 0, y));
+            norms.push_back(Vector3(0,1,0));
+        }
+    }
+    std::vector<unsigned int> indices;
+    for (int j = 0; j < ny; j++) {
+        for (int i = 0; i < nx; i++) {
+            // L\ triangle
+            indices.push_back((i+0)+(j+0)*(nx+1));
+            indices.push_back((i+1)+(j+0)*(nx+1));
+            indices.push_back((i+0)+(j+1)*(nx+1));
+            // \7 triangle
+            indices.push_back((i+1)+(j+0)*(nx+1));
+            indices.push_back((i+1)+(j+1)*(nx+1));
+            indices.push_back((i+0)+(j+1)*(nx+1));
+        }
+    }
+    ground_mesh_.SetIndices(indices);
+    ground_mesh_.SetVertices(verts);
+    ground_mesh_.SetNormals(norms);
+    ground_mesh_.UpdateGPUMemory();
+    ground_edge_mesh_.CreateFromMesh(ground_mesh_);
+
+    
+    // load textures and shaders
+    diffuse_ramp_.InitFromFile(Platform::FindFile("toonDiffuse.png", search_path));
+    specular_ramp_.InitFromFile(Platform::FindFile("toonSpecular.png", search_path));
+    
+    artsy_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("artsy.vert", search_path));
+    artsy_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("artsy.frag", search_path));
+    artsy_shaderprog_.LinkProgram();
+    
+    outline_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("outline.vert", search_path));
+    outline_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("outline.frag", search_path));
+    outline_shaderprog_.LinkProgram();
+}
+
+
+
+
+// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+// device coordinates) to a 3D point on the ground.  Returns true and sets ground_point
+// to be equal to the result if the conversion is successful.  Returns false if
+// the screen point does not project onto the ground.
+bool Ground::ScreenPtHitsGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                              const Point2 &normalized_screen_pt, Point3 *ground_point)
+{
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    
+    Point3 pt3d = GfxMath::ScreenToNearPlane(view_matrix, proj_matrix, normalized_screen_pt);
+    Ray ray(eye, (pt3d - eye).ToUnit());
+    float i_time;
+    int i_tri;
+    return ray.FastIntersectMesh(&ground_mesh_, &i_time, ground_point, &i_tri);
+}
+
+
+
+
+/** This implements the "h" term used in the equations described in section 4.5 of the
+ paper. Three arguments are needed:
+ 1. projection_plane_normal: We need to know where the projection plane is in 3-space
+    Since a plane can be defined by a point within the plane and a normal, we use
+    this normal together with the 3rd argument to the function to define the projection
+    plane described in the paper.
+ 2. silhouette_curve: As described in the paper, the silhouette curve is a 3D version
+    of the curve the user draws with the mouse.  It is formed by projecting the
+    original 2D screen-space curve onto the 3D projection plane.
+ 3. closest_pt_in_plane: As described in the paper, this is the closest point within
+    the projection plane to the vertex of the mesh that we want to modify.  In other
+    words, it is the perpendicular projection of the vertex we want to modify onto
+    the projection plane.
+ */
+float hfunc(const Vector3 projection_plane_normal, const std::vector<Point3> &silhouette_curve, const Point3 &closest_pt_in_plane) {
+    // define the y axis for a "plane space" coordinate system as a world space vector
+    Vector3 plane_y = Vector3(0,1,0);
+    // define the x axis for a "plane space" coordinate system as a world space vector
+    Vector3 plane_x = plane_y.Cross(projection_plane_normal).ToUnit();
+    // define the origin for a "plane space" coordinate system as the first point in the curve
+    Point3 origin = silhouette_curve[0];
+    
+    // loop over line segments in the curve, find the one that lies over the point by
+    // comparing the "plane space" x value for the start and end of the line segment
+    // to the "plane space" x value for the closest point to the vertex that lies
+    // in the projection plane.
+    float x_target = (closest_pt_in_plane - origin).Dot(plane_x);
+    for (int i=1; i<silhouette_curve.size(); i++) {
+        float x_start = (silhouette_curve[(size_t)i-1] - origin).Dot(plane_x);
+        float x_end = (silhouette_curve[i] - origin).Dot(plane_x);
+        if ((x_start <= x_target) && (x_target <= x_end)) {
+            float alpha = (x_target - x_start) / (x_end - x_start);
+            float y_curve = silhouette_curve[(size_t)i-1][1] + alpha*(silhouette_curve[i][1] - silhouette_curve[(size_t)i-1][1]);
+            return y_curve - closest_pt_in_plane[1];
+        }
+        else if ((x_end <= x_target) && (x_target <= x_start)) {
+            float alpha = (x_target - x_end) / (x_start - x_end);
+            float y_curve = silhouette_curve[i][1] + alpha*(silhouette_curve[(size_t)i-1][1] - silhouette_curve[i][1]);
+            return y_curve - closest_pt_in_plane[1];
+        }
+    }
+    
+    // here return 0 because the point does not lie under the curve.
+    return 0.0;
+}
+
+
+
+
+/// Modifies the vertices of the ground mesh to create a hill or valley based
+/// on the input stroke.  The 2D path of the stroke on the screen is passed
+/// in, this is the centerline of the stroke mesh that is actually drawn on
+/// the screen while the user is drawing.
+void Ground::ReshapeGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                           const std::vector<Point2> &stroke2d)
+{
+    // TODO: Deform the 3D ground mesh according to the algorithm described in the
+    // Cohen et al. Harold paper.
+    
+    // You might need the eye point and the look vector, these can be determined
+    // from the view matrix as follows:
+    Matrix4 camera_matrix = view_matrix.Inverse();
+    Point3 eye = camera_matrix.ColumnToPoint3(3);
+    Vector3 look = -camera_matrix.ColumnToVector3(2);
+    
+    
+    
+    // There are 3 major steps to the algorithm, outlined here:
+    
+    // 1. Define a plane to project the stroke onto.  The first and last points
+    // of the stroke are guaranteed to project onto the ground plane.  The plane
+    // should pass through these two points on the ground.  The plane should also
+    // have a normal vector that points toward the camera and is parallel to the
+    // ground plane.
+
+    
+    
+    
+    
+    // 2. Project the 2D stroke into 3D so that it lies on the "projection plane"
+    // defined in step 1.
+    
+    
+    
+    
+    
+    // 3. Loop through all of the vertices of the ground mesh, and adjust the
+    // height of each based on the equations in section 4.5 of the paper, also
+    // repeated in the assignment handout.  The equations rely upon a function
+    // h(), and we have implemented that for you as hfunc() defined above in
+    // this file.  The basic structure of the loop you will need is here:
+    std::vector<Point3> new_verts;
+    for (int i=0; i<ground_mesh_.num_vertices(); i++) {
+        Point3 P = ground_mesh_.read_vertex_data(i); // original vertex
+
+        // adjust P according to equations...
+        
+        
+        
+        
+        
+        new_verts.push_back(P);
+    }
+    ground_mesh_.SetVertices(new_verts);
+    ground_mesh_.CalcPerVertexNormals();
+    ground_mesh_.UpdateGPUMemory();
+    ground_edge_mesh_.CreateFromMesh(ground_mesh_);
+}
+
+
+
+
+/// Draws the ground mesh with toon shading
+void Ground::Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix, const Color &ground_color) {
+    // Lighting parameters
+    Color Ia(1.0f, 1.0f, 1.0f, 1.0f);
+    Color Id(1.0f, 1.0f, 1.0f, 1.0f);
+    Color Is(1.0f, 1.0f, 1.0f, 1.0f);
+    
+    // Material parameters
+    Color ka = ground_color;
+    Color kd(0.4f, 0.4f, 0.4f, 1.0f);
+    Color ks(0.6f, 0.6f, 0.6f, 1.0f);
+    float s = 50.0f;
+    
+    // Precompute matrices needed in the shader
+    Matrix4 model_matrix; // identity
+    Matrix4 modelview_matrix = view_matrix * model_matrix;
+    Matrix4 normal_matrix = modelview_matrix.Inverse().Transpose();
+    Point3 light_in_eye_space = view_matrix * light_pos_;
+    
+    // Make sure the default option to only draw front facing triangles is set
+    glEnable(GL_CULL_FACE);
+    
+    
+    // Draw the ground using the artsy shader
+    artsy_shaderprog_.UseProgram();
+    artsy_shaderprog_.SetUniform("modelViewMatrix", modelview_matrix);
+    artsy_shaderprog_.SetUniform("normalMatrix", normal_matrix);
+    artsy_shaderprog_.SetUniform("projectionMatrix", proj_matrix);
+    artsy_shaderprog_.SetUniform("ka", ka);
+    artsy_shaderprog_.SetUniform("kd", kd);
+    artsy_shaderprog_.SetUniform("ks", ks);
+    artsy_shaderprog_.SetUniform("s", s);
+    artsy_shaderprog_.SetUniform("lightPosition", light_in_eye_space);
+    artsy_shaderprog_.SetUniform("Ia", Ia);
+    artsy_shaderprog_.SetUniform("Id", Id);
+    artsy_shaderprog_.SetUniform("Is", Is);
+    artsy_shaderprog_.BindTexture("diffuseRamp", diffuse_ramp_);
+    artsy_shaderprog_.BindTexture("specularRamp", specular_ramp_);
+    ground_mesh_.Draw();
+    artsy_shaderprog_.StopProgram();
+    
+    // And, draw silhouette edges for the ground using the outline shader
+    glDisable(GL_CULL_FACE);
+    glEnable(GL_POLYGON_OFFSET_FILL);
+    glPolygonOffset(1,1);
+    static const float thickness = 0.2f;
+    outline_shaderprog_.UseProgram();
+    outline_shaderprog_.SetUniform("modelViewMatrix", modelview_matrix);
+    outline_shaderprog_.SetUniform("normalMatrix", normal_matrix);
+    outline_shaderprog_.SetUniform("projectionMatrix", proj_matrix);
+    outline_shaderprog_.SetUniform("thickness", thickness);
+    ground_edge_mesh_.Draw();
+    outline_shaderprog_.StopProgram();
+    
+
+    
+    // This can be useful for debugging, but it is extremely slow to draw.
+    // Before uncommenting this, it's recommended to turn down the resolution
+    // of the ground mesh by adjusting the nx and ny constants inside Init().
+    /**
+     // draw lines around each triangle
+     for (int t=0; t<ground_mesh_.num_triangles(); t++) {
+         std::vector<unsigned int> indices = ground_mesh_.triangle_vertices(t);
+         std::vector<Point3> loop;
+         loop.push_back(ground_mesh_.vertex(indices[0]));
+         loop.push_back(ground_mesh_.vertex(indices[1]));
+         loop.push_back(ground_mesh_.vertex(indices[2]));
+         qs_.DrawLines(model_matrix, view_matrix, proj_matrix, Color(0.7,0.7,0.7), loop, QuickShapes::LinesType::LINE_LOOP, 0.01);
+     }
+     
+     // draw normals
+     for (int i=0; i<ground_mesh_.num_vertices(); i++) {
+         Point3 p1 = ground_mesh_.vertex(i);
+         Point3 p2 = p1 + 0.5*ground_mesh_.normal(i);
+         qs_.DrawLineSegment(model_matrix, view_matrix, proj_matrix, Color(0.7,0.7,0.7), p1, p2, 0.01);
+     }
+    **/
+}
+
diff --git a/dev/a6-harold/ground.h b/dev/a6-harold/ground.h
new file mode 100644
index 0000000..0cc18dd
--- /dev/null
+++ b/dev/a6-harold/ground.h
@@ -0,0 +1,63 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#ifndef GROUND_H_
+#define GROUND_H_
+
+#include <mingfx.h>
+using namespace mingfx;
+
+#include "edge_mesh.h"
+
+/** The ground is represented with a triangle mesh.  2D "screen space" strokes
+ are used to modify the vertices based on user input so that the user can create
+ a 3D landscape of hills and valleys.
+ */
+class Ground {
+public:
+    Ground();
+    virtual ~Ground();
+    
+    /// Call from InitOpenGL() to initialize shaders, etc.
+    void Init(const std::vector<std::string> &search_path);
+    
+    /// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+    /// device coordinates) to a 3D point on the ground.  Returns true and sets ground_point
+    /// to be equal to the result if the conversion is successful.  Returns false if
+    /// the screen point does not project onto the ground.
+    bool ScreenPtHitsGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                          const Point2 &normalized_screen_pt, Point3 *ground_point);
+
+    /// Modifies the vertices of the ground mesh to create a hill or valley based
+    /// on the input stroke.  The 2D path of the stroke on the screen is passed
+    /// in, this is the centerline of the stroke mesh that is actually drawn on
+    /// the screen while the user is drawing.
+    void ReshapeGround(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                       const std::vector<Point2> &stroke2d);
+    
+    /// Draws the ground mesh with toon shading
+    void Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix, const Color &ground_color);
+    
+    
+    Mesh* mesh_ptr();
+    
+private:
+    
+    // This is the actual triangle mesh for the ground
+    Mesh ground_mesh_;
+    // We also maintain a corresponding "edge mesh" in order to do the
+    // silhouette outlines like in assignment 5
+    EdgeMesh ground_edge_mesh_;
+    
+    // The ground rendering is based on the artsy shader from assignment 5
+    ShaderProgram artsy_shaderprog_;
+    ShaderProgram outline_shaderprog_;
+    Texture2D diffuse_ramp_;
+    Texture2D specular_ramp_;
+    Point3 light_pos_;
+    
+    // for debugging only
+    QuickShapes qs_;
+};
+
+#endif
diff --git a/dev/a6-harold/harold_app.cc b/dev/a6-harold/harold_app.cc
new file mode 100644
index 0000000..abf5c4d
--- /dev/null
+++ b/dev/a6-harold/harold_app.cc
@@ -0,0 +1,278 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "harold_app.h"
+#include "config.h"
+
+#include <iostream>
+#include <sstream>
+
+
+HaroldApp::HaroldApp() : GraphicsApp(1024,768, "Harold"),
+    drawing_state_(DRAWING_NONE),
+    sky_color_(1,1,1), ground_color_(0.25, 0, 0.25), crayon_color_(0.5,0,0.5)
+{
+    // Define a search path for finding data files (images and shaders)
+    search_path_.push_back(".");
+    search_path_.push_back("./data");
+    search_path_.push_back("./shaders");
+    search_path_.push_back(DATA_DIR_INSTALL);
+    search_path_.push_back(DATA_DIR_BUILD);
+    search_path_.push_back(SHADERS_DIR_INSTALL);
+    search_path_.push_back(SHADERS_DIR_BUILD);
+}
+
+
+HaroldApp::~HaroldApp() {
+}
+
+
+void HaroldApp::InitNanoGUI() {
+    // Setup the GUI window
+    nanogui::Window *window = new nanogui::Window(screen(), "Harold's Crayons");
+    window->setPosition(Eigen::Vector2i(10, 10));
+    window->setSize(Eigen::Vector2i(200,100));
+    window->setLayout(new nanogui::GroupLayout());
+
+    new nanogui::Label(window, "Crayon Color", "sans-bold");
+    auto cp1 = new nanogui::ColorPicker(window,
+        nanogui::Color((int)(255.0*crayon_color_[0]),
+                       (int)(255.0*crayon_color_[1]),
+                       (int)(255.0*crayon_color_[2]), 255)
+    );
+    cp1->setFixedSize({100, 20});
+    cp1->setFinalCallback([this](const nanogui::Color &c) {
+        crayon_color_ = Color(c.r(), c.g(), c.b(), c.w());
+    });
+
+    new nanogui::Label(window, "Sky Color", "sans-bold");
+    auto cp2 = new nanogui::ColorPicker(window,
+        nanogui::Color((int)(255.0*sky_color_[0]),
+                       (int)(255.0*sky_color_[1]),
+                       (int)(255.0*sky_color_[2]), 255)
+    );
+    cp2->setFixedSize({100, 20});
+    cp2->setFinalCallback([this](const nanogui::Color &c) {
+        sky_color_ = Color(c.r(), c.g(), c.b(), c.w());
+    });
+
+    new nanogui::Label(window, "Ground Color", "sans-bold");
+    auto cp3 = new nanogui::ColorPicker(window,
+        nanogui::Color((int)(255.0*ground_color_[0]),
+                       (int)(255.0*ground_color_[1]),
+                       (int)(255.0*ground_color_[2]), 255)
+    );
+    cp3->setFixedSize({100, 20});
+    cp3->setFinalCallback([this](const nanogui::Color &c) {
+        ground_color_ = Color(c.r(), c.g(), c.b(), c.w());
+    });
+
+    screen()->performLayout();
+}
+
+
+void HaroldApp::InitOpenGL() {
+    // Set up the camera in a good position to see the entire field
+    cam_.set_view_matrix(Matrix4::LookAt(Point3(0,2,10), Point3(0,2,0), Vector3(0,1,0)));
+    proj_matrix_ = Matrix4::Perspective(60, aspect_ratio(), 0.1f, 1600.0f);
+    glClearColor(0.7f, 0.7f, 0.7f, 1.0f);
+    
+    stroke2d_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("stroke2d.vert", search_path_));
+    stroke2d_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("stroke2d.frag", search_path_));
+    stroke2d_shaderprog_.LinkProgram();
+    
+    stroke3d_shaderprog_.AddVertexShaderFromFile(Platform::FindFile("stroke3d.vert", search_path_));
+    stroke3d_shaderprog_.AddFragmentShaderFromFile(Platform::FindFile("stroke3d.frag", search_path_));
+    stroke3d_shaderprog_.LinkProgram();
+    
+    ground_.Init(search_path_);
+    sky_.Init(&stroke3d_shaderprog_);
+    billboards_.Init(&stroke3d_shaderprog_);
+}
+
+
+
+void HaroldApp::AddToStroke(const Point2 &normalized_screen_pt) {
+    // the stroke2d_ array stores the raw 2D screen coordinates of the
+    // centerline of the stroke
+    stroke2d_.push_back(normalized_screen_pt);
+    
+    // the mesh is a triangle strip that follows the centerline
+    // we need at least 2 samples before we can create triangles
+    if (stroke2d_.size() >= 2) {
+        const float half_stroke_width = 0.01f;
+        std::vector<Point3> verts;
+        std::vector<unsigned int> indices;
+        Point3 last_pt = Point3(stroke2d_[0][0], stroke2d_[0][1], 0);
+        Point3 pt = Point3(stroke2d_[1][0], stroke2d_[1][1], 0);
+        Vector3 tangent = (pt - last_pt).ToUnit();
+        Vector3 cotangent = tangent.Cross(Vector3::UnitZ());
+        verts.push_back(last_pt - half_stroke_width*cotangent);
+        verts.push_back(last_pt + half_stroke_width*cotangent);
+        for (int i=1; i<stroke2d_.size(); i++) {
+            pt = Point3(stroke2d_[i][0], stroke2d_[i][1], 0);
+            tangent = (pt - last_pt).ToUnit();
+            cotangent = tangent.Cross(Vector3::UnitZ());
+            
+            verts.push_back(pt - half_stroke_width*cotangent);
+            verts.push_back(pt + half_stroke_width*cotangent);
+            
+            indices.push_back((int)verts.size()-4);
+            indices.push_back((int)verts.size()-3);
+            indices.push_back((int)verts.size()-2);
+
+            indices.push_back((int)verts.size()-3);
+            indices.push_back((int)verts.size()-1);
+            indices.push_back((int)verts.size()-2);
+            
+            last_pt = pt;
+        }
+        stroke2d_mesh_.SetVertices(verts);
+        stroke2d_mesh_.SetIndices(indices);
+        stroke2d_mesh_.UpdateGPUMemory();
+    }
+}
+
+
+
+// This function is called at the start of each new crayon stroke
+void HaroldApp::OnLeftMouseDown(const Point2 &mouse_in_pixels) {
+    // Add to the stroke_mesh_, which is a 2D triangle strip used to draw the user's
+    // crayon stroke on the screen.
+    Point2 mouse_in_ndc = PixelsToNormalizedDeviceCoords(mouse_in_pixels);
+    AddToStroke(mouse_in_ndc);
+    
+    
+    // Next, try to figure out what we are drawing based on where the stroke originated.
+    Point3 i_point;
+    edit_billboard_id_ = billboards_.IntersectBillboard(cam_.view_matrix(), proj_matrix_, mouse_in_ndc);
+    if (edit_billboard_id_ >= 0) {
+        // If the mouse starts on an existing billboard, then we are editing the billboard.
+        drawing_state_ = DrawingState::DRAWING_BILLBOARD_EDIT;
+    }
+    else if (ground_.ScreenPtHitsGround(cam_.view_matrix(), proj_matrix_, mouse_in_ndc, &i_point)) {
+        // If the mouse starts on the ground, then we could be about to edit the
+        // ground, OR we might be creating a new billboard.  We won't know for sure
+        // until the user releases the mouse and we can check to see whether the
+        // stroke also ends on the ground.
+        drawing_state_ = DrawingState::DRAWING_GROUND_OR_BILLBOARD;
+    }
+    else {
+        // Otherwise, we must be drawing a stroke in the sky.
+        drawing_state_ = DrawingState::DRAWING_SKY;
+    }
+}
+
+
+// This function is called once each frame while the user is drawing with the crayon
+void HaroldApp::OnLeftMouseDrag(const Point2 &mouse_in_pixels, const Vector2 &delta_in_pixels) {
+    // Add to the stroke_mesh_, which is a 2D triangle strip used to draw the user's
+    // crayon stroke on the screen.
+    Point2 mouse_in_ndc = PixelsToNormalizedDeviceCoords(mouse_in_pixels);
+    AddToStroke(mouse_in_ndc);
+}
+
+
+// This function is called at the end of each stroke
+void HaroldApp::OnLeftMouseUp(const Point2 &mouse_in_pixels) {
+    
+    // If we are in the temporary drawing_ground_or_billboard state, then we need
+    // to do a final check now to see if the stroke ended on the ground or not.
+    // If it did, then we interpret the stroke as drawing_ground.  Otherwise, we
+    // treat it as creating a new billboard.
+    if (drawing_state_ == DrawingState::DRAWING_GROUND_OR_BILLBOARD) {
+        // The stroke was started on the ground, does it also end on the ground?
+        Point2 mouse_in_ndc = PixelsToNormalizedDeviceCoords(mouse_in_pixels);
+        Point3 i_point;
+        if (ground_.ScreenPtHitsGround(cam_.view_matrix(), proj_matrix_, mouse_in_ndc, &i_point)) {
+            drawing_state_ = DrawingState::DRAWING_GROUND;
+        }
+        else {
+            drawing_state_ = DrawingState::DRAWING_BILLBOARD;
+        }
+    }
+    
+    
+    // Now, the action to take in terms of what geometry to add or modify in
+    // the scene depends entirely on the drawing state:
+    if (drawing_state_ == DrawingState::DRAWING_SKY) {
+        sky_.AddSkyStroke(cam_.view_matrix(), proj_matrix_, stroke2d_mesh_, crayon_color_);
+    }
+    else if (drawing_state_ == DrawingState::DRAWING_BILLBOARD) {
+        billboards_.AddBillboardStroke(cam_.view_matrix(), proj_matrix_, stroke2d_, stroke2d_mesh_, crayon_color_, &ground_);
+    }
+    else if (drawing_state_ == DrawingState::DRAWING_BILLBOARD_EDIT) {
+        billboards_.AddToBillboard(cam_.view_matrix(), proj_matrix_, edit_billboard_id_, stroke2d_mesh_, crayon_color_);
+    }
+    else if (drawing_state_ == DrawingState::DRAWING_GROUND) {
+        if (stroke2d_.size() < 6) {
+            std::cout << "Stroke is too short, try again." << std::endl;
+        }
+        else {
+            ground_.ReshapeGround(cam_.view_matrix(), proj_matrix_, stroke2d_);
+        }
+    }
+    
+    
+    // Done with this stroke.  Clear the 2d stroke and its mesh and reset the drawing state
+    stroke2d_.clear();
+    stroke2d_mesh_ = Mesh();
+    drawing_state_ = DrawingState::DRAWING_NONE;
+}
+
+
+// You can look around, like in minecraft, by dragging with the right mouse button.
+void HaroldApp::OnRightMouseDrag(const Point2 &mouse_in_pixels, const Vector2 &delta_in_pixels) {
+    Vector2 delta_in_ndc = PixelsToNormalizedDeviceCoords(delta_in_pixels);
+    cam_.OnMouseMove(delta_in_ndc);
+}
+
+
+void HaroldApp::UpdateSimulation(double dt)  {
+    if (drawing_state_ == DrawingState::DRAWING_NONE) {
+        // When walking around using the arrow keys we need to adjust the height
+        // of the virtual camera when we walk up a hill.  To do that, we shoot
+        // a ray straight down from the eye point to the ground, find the point
+        // of intersection on the ground, and then set the camera height to be
+        // 2.0 meters above this.
+        Ray ray(cam_.eye(), -Vector3::UnitY());
+        float i_time;
+        Point3 i_pt;
+        int i_tri;
+        if (ray.FastIntersectMesh(ground_.mesh_ptr(), &i_time, &i_pt, &i_tri)) {
+            float height = 2.0f + i_pt[1]; // 2 meters above the gound
+            cam_.UpdateHeight(height);
+        }
+        cam_.UpdateSimulation(dt, window());
+        
+        
+        // The billboards also need to be updated to face the current camera
+        billboards_.UpdateBillboardRotations(cam_.eye());
+    }
+}
+
+
+void HaroldApp::DrawUsingOpenGL() {
+    // Clear the screen using the current sky color
+    glClearColor(sky_color_[0], sky_color_[1], sky_color_[2], 1);
+    
+    // Draw the sky strokes
+    sky_.Draw(cam_.view_matrix(), proj_matrix_);
+    
+    // Draw the ground mesh
+    ground_.Draw(cam_.view_matrix(), proj_matrix_, ground_color_);
+    
+    // Draw the billboards
+    billboards_.Draw(cam_.view_matrix(), proj_matrix_);
+
+    
+    // If we are currently drawing (indicated by the stroke mesh containing >0
+    // triangles), then draw the 2D triangle strip mesh for the crayon stroke
+    if (stroke2d_mesh_.num_triangles() > 0) {
+        stroke2d_shaderprog_.UseProgram();
+        stroke2d_shaderprog_.SetUniform("strokeColor", crayon_color_);
+        stroke2d_mesh_.Draw();
+        stroke2d_shaderprog_.StopProgram();
+    }
+}
+
diff --git a/dev/a6-harold/harold_app.h b/dev/a6-harold/harold_app.h
new file mode 100644
index 0000000..801a49a
--- /dev/null
+++ b/dev/a6-harold/harold_app.h
@@ -0,0 +1,120 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#ifndef HAROLD_APP_H_
+#define HAROLD_APP_H_
+
+#include <mingfx.h>
+using namespace mingfx;
+
+#include "billboards.h"
+#include "edge_mesh.h"
+#include "ground.h"
+#include "sky.h"
+
+#include <string>
+#include <vector>
+
+
+/** Main application class for the Harold assignment, which is a partial
+ implementation of the Cohen et al. paper.
+ */
+class HaroldApp : public GraphicsApp {
+public:
+    
+    HaroldApp();
+    virtual ~HaroldApp();
+    
+    // These are used for drawing
+    void OnLeftMouseDown(const Point2 &pos);
+    void OnLeftMouseDrag(const Point2 &pos, const Vector2 &delta);
+    void OnLeftMouseUp(const Point2 &pos);
+    
+    // These are used for walking around and looking (i.e., camera movement)
+    void OnRightMouseDrag(const Point2 &pos, const Vector2 &delta);
+    void UpdateSimulation(double dt);
+    
+    // Adds the 2D point to stroke2d_, which holds the centerline of the user's
+    // drawn stroke.  Also updates stroke2d_mesh_, which is a 2D triangle strip
+    // used to actually draw the stroke on the screen.
+    void AddToStroke(const Point2 &normalized_screen_pt);
+
+    void InitNanoGUI();
+    void InitOpenGL();
+    
+    void DrawUsingOpenGL();
+    
+private:
+    
+    // user input from the mouse is interpreted differently based upon where the
+    // stroke originates and where it ends.  we can model this as a simple state
+    // machine
+    enum DrawingState {
+        // left mouse button is up, not currently drawing
+        DRAWING_NONE,
+        
+        // stroke started in the sky, currently adding a sky stroke
+        DRAWING_SKY,
+        
+        // stroke started on a billboard, currently editing that billboard
+        DRAWING_BILLBOARD_EDIT,
+
+        // temporary state for between mouse down and mouse up -- here, we know
+        // the stroke started on the ground, but not yet sure if it will end on
+        // the ground or in the sky
+        DRAWING_GROUND_OR_BILLBOARD,
+ 
+        // stroke ended on the ground, currently editing the ground
+        DRAWING_GROUND,
+        
+        // stroke ended in the sky, currently creating a new billboard
+        DRAWING_BILLBOARD,
+    };
+    DrawingState drawing_state_;
+    
+    // the centerline of the stroke dragged out by the mouse on the screen
+    std::vector<Point2> stroke2d_;
+
+    // a 2d triangle strip mesh for drawing the stroke on the filmplane
+    Mesh stroke2d_mesh_;
+    
+    // The ground mesh and functionality to draw and edit the ground.
+    Ground ground_;
+    
+    // Sky strokes and functionality to add more strokes to the sky
+    Sky sky_;
+    
+    // Billboard strokes and functionality to add more billboards, including
+    // editing them by adding on to an existing billboard
+    Billboards billboards_;
+    
+    // when in the DRAWING_BILLBOARD_EDIT state, this holds the id of the
+    // billboard that is currently being edited.
+    int edit_billboard_id_;
+    
+
+    // Stroke shaders do not use any lighting, just transform vertices and then
+    // render the triangle strip for the stroke in the appropriate color. The
+    // 2D shader program is used in this class.  The 3D is created here so that
+    // there is only one copy for the whole application, but it is used both the
+    // sky and billboard classes.
+    ShaderProgram stroke2d_shaderprog_;
+    ShaderProgram stroke3d_shaderprog_;
+
+    // This implements something like the camera controls in minecraft.  You can
+    // walk around using the arrow keys or ASWZ keys.  You can also move your
+    // head to look around by dragging with the right mouse button.  Internally,
+    // the camera creates a view matrix.
+    CraftCam cam_;
+    Matrix4 proj_matrix_;
+    
+    // A list of paths to search for data files (images and shaders)
+    std::vector<std::string> search_path_;
+    
+    // Current colors set by the GUI
+    Color sky_color_;
+    Color ground_color_;
+    Color crayon_color_;
+};
+
+#endif
\ No newline at end of file
diff --git a/dev/a6-harold/main.cc b/dev/a6-harold/main.cc
new file mode 100644
index 0000000..b672b01
--- /dev/null
+++ b/dev/a6-harold/main.cc
@@ -0,0 +1,10 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "harold_app.h"
+
+int main(int argc, const char *argv[]) {
+    HaroldApp app;
+    app.Run();
+    return 0;
+}
diff --git a/dev/a6-harold/shaders/artsy.frag b/dev/a6-harold/shaders/artsy.frag
new file mode 100644
index 0000000..403009d
--- /dev/null
+++ b/dev/a6-harold/shaders/artsy.frag
@@ -0,0 +1,29 @@
+#version 330
+
+in vec3 Position;
+in vec3 Normal;
+
+out vec4 color;
+
+uniform vec3 lightPosition;
+uniform vec4 Ia, Id, Is;
+
+uniform vec4 ka, kd, ks;
+uniform float s;
+
+uniform sampler2D diffuseRamp;
+uniform sampler2D specularRamp;
+
+
+void main() {
+    vec3 l = normalize(lightPosition.xyz - Position);
+    vec3 n = normalize(Normal);
+    vec3 e = normalize(-Position);
+    vec3 h = normalize(e + l);
+    float diffuse = (dot(l,n) + 1)/2;
+    float specular = pow(max(dot(n,h),0), s);
+    color = ka*Ia
+          + kd*Id*texture(diffuseRamp, vec2(diffuse,0))
+          + ks*Is*texture(specularRamp, vec2(specular,0));
+    color.a = 1;
+}
diff --git a/dev/a6-harold/shaders/artsy.vert b/dev/a6-harold/shaders/artsy.vert
new file mode 100644
index 0000000..cd9b998
--- /dev/null
+++ b/dev/a6-harold/shaders/artsy.vert
@@ -0,0 +1,17 @@
+#version 330
+
+uniform mat4 modelViewMatrix;
+uniform mat4 normalMatrix;
+uniform mat4 projectionMatrix;
+
+layout(location = 0) in vec3 vertex;
+layout(location = 1) in vec3 normal;
+
+out vec3 Position;
+out vec3 Normal;
+
+void main() {
+    Position = (modelViewMatrix * vec4(vertex,1)).xyz;
+    Normal = normalize((normalMatrix * vec4(normal,0)).xyz);
+    gl_Position = projectionMatrix * modelViewMatrix * vec4(vertex,1);
+}
diff --git a/dev/a6-harold/shaders/outline.frag b/dev/a6-harold/shaders/outline.frag
new file mode 100644
index 0000000..096721d
--- /dev/null
+++ b/dev/a6-harold/shaders/outline.frag
@@ -0,0 +1,7 @@
+#version 330
+
+out vec4 color;
+
+void main() {
+    color = vec4(0,0,0, 1);
+}
diff --git a/dev/a6-harold/shaders/outline.vert b/dev/a6-harold/shaders/outline.vert
new file mode 100644
index 0000000..a6073e5
--- /dev/null
+++ b/dev/a6-harold/shaders/outline.vert
@@ -0,0 +1,23 @@
+#version 330
+
+uniform mat4 modelViewMatrix;
+uniform mat4 normalMatrix;
+uniform mat4 projectionMatrix;
+uniform float thickness;
+
+layout(location = 0) in vec3 vertex;
+layout(location = 1) in vec3 normal;
+layout(location = 2) in vec3 leftNormal;
+layout(location = 3) in vec3 rightNormal;
+
+void main() {
+    vec3 p = (modelViewMatrix * vec4(vertex,1)).xyz;
+    vec3 e = -p;
+    vec3 nl = (normalMatrix * vec4(leftNormal,0)).xyz;
+    vec3 nr = (normalMatrix * vec4(rightNormal,0)).xyz;
+    vec3 v = vertex;
+    if (dot(e,nl) * dot(e,nr) < 0.0) {
+       v += thickness*normal;
+    }
+    gl_Position = projectionMatrix * modelViewMatrix * vec4(v,1);
+}
diff --git a/dev/a6-harold/shaders/stroke2d.frag b/dev/a6-harold/shaders/stroke2d.frag
new file mode 100644
index 0000000..2dd7efa
--- /dev/null
+++ b/dev/a6-harold/shaders/stroke2d.frag
@@ -0,0 +1,9 @@
+#version 330
+
+uniform vec4 strokeColor;
+
+out vec4 color;
+
+void main() {
+    color = strokeColor;
+}
diff --git a/dev/a6-harold/shaders/stroke2d.vert b/dev/a6-harold/shaders/stroke2d.vert
new file mode 100644
index 0000000..e40fdec
--- /dev/null
+++ b/dev/a6-harold/shaders/stroke2d.vert
@@ -0,0 +1,7 @@
+#version 330
+
+layout(location = 0) in vec3 vertex;
+
+void main() {
+    gl_Position = vec4(vertex,1);
+}
diff --git a/dev/a6-harold/shaders/stroke3d.frag b/dev/a6-harold/shaders/stroke3d.frag
new file mode 100644
index 0000000..2dd7efa
--- /dev/null
+++ b/dev/a6-harold/shaders/stroke3d.frag
@@ -0,0 +1,9 @@
+#version 330
+
+uniform vec4 strokeColor;
+
+out vec4 color;
+
+void main() {
+    color = strokeColor;
+}
diff --git a/dev/a6-harold/shaders/stroke3d.vert b/dev/a6-harold/shaders/stroke3d.vert
new file mode 100644
index 0000000..d333c4f
--- /dev/null
+++ b/dev/a6-harold/shaders/stroke3d.vert
@@ -0,0 +1,10 @@
+#version 330
+
+uniform mat4 modelViewMatrix;
+uniform mat4 projectionMatrix;
+
+layout(location = 0) in vec3 vertex;
+
+void main() {
+    gl_Position = projectionMatrix * modelViewMatrix * vec4(vertex,1);
+}
diff --git a/dev/a6-harold/sky.cc b/dev/a6-harold/sky.cc
new file mode 100644
index 0000000..0819ebe
--- /dev/null
+++ b/dev/a6-harold/sky.cc
@@ -0,0 +1,74 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#include "sky.h"
+
+
+Sky::Sky() {
+    
+}
+
+
+Sky::~Sky() {
+    
+}
+
+void Sky::Init(ShaderProgram *stroke3d_shaderprog) {
+    stroke3d_shaderprog_ = stroke3d_shaderprog;
+}
+
+
+/// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+/// device coordinates) to a 3D point on the "sky", which is really a huge sphere
+/// (radius = 1500) that the viewer is inside.  This function should always return
+/// true since any screen point can successfully be projected onto the sphere.
+/// sky_point is set to the resulting 3D point.  Note, this function only checks
+/// to see if the ray passing through the screen point intersects the sphere; it
+/// does not check to see if the ray hits the ground or anything else first.
+bool Sky::ScreenPtHitsSky(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                        const Point2 &normalized_screen_pt, Point3 *sky_point)
+{
+    // TODO: Stitch together your worksheet implementation of this method
+    return true;
+}
+
+
+
+
+/// Creates a new sky stroke mesh by projecting each vertex of the 2D mesh
+/// onto the sky dome and saving the result as a new 3D mesh.
+void Sky::AddSkyStroke(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                       const Mesh &stroke2d_mesh, const Color &stroke_color)
+{
+    // TODO: Create a new SkyStroke and add it to the strokes_ array.
+
+
+
+
+
+
+
+
+
+
+}
+
+
+/// Draws all of the sky strokes
+void Sky::Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix) {
+
+    // Precompute matrices needed in the shader
+    Matrix4 model_matrix; // identity
+    Matrix4 modelview_matrix = view_matrix * model_matrix;
+    
+    // Draw sky meshes
+    stroke3d_shaderprog_->UseProgram();
+    stroke3d_shaderprog_->SetUniform("modelViewMatrix", modelview_matrix);
+    stroke3d_shaderprog_->SetUniform("projectionMatrix", proj_matrix);
+    for (int i=0; i<strokes_.size(); i++) {
+        stroke3d_shaderprog_->SetUniform("strokeColor", strokes_[i].color);
+        strokes_[i].mesh.Draw();
+    }
+    stroke3d_shaderprog_->StopProgram();
+}
+
diff --git a/dev/a6-harold/sky.h b/dev/a6-harold/sky.h
new file mode 100644
index 0000000..06fcca1
--- /dev/null
+++ b/dev/a6-harold/sky.h
@@ -0,0 +1,52 @@
+/** CSci-4611 Assignment 6: Harold
+ */
+
+#ifndef SKY_H_
+#define SKY_H_
+
+#include <mingfx.h>
+using namespace mingfx;
+
+/** Creates, holds, and draws all of the strokes on the sky.
+ */
+class Sky {
+public:
+    Sky();
+    virtual ~Sky();
+    
+    void Init(ShaderProgram *stroke3d_shaderprog);
+    
+    /// Projects a 2D normalized screen point (e.g., the mouse position in normalized
+    /// device coordinates) to a 3D point on the "sky", which is really a huge sphere
+    /// (radius = 1500) that the viewer is inside.  This function should always return
+    /// true since any screen point can successfully be projected onto the sphere.
+    /// sky_point is set to the resulting 3D point.  Note, this function only checks
+    /// to see if the ray passing through the screen point intersects the sphere; it
+    /// does not check to see if the ray hits the ground or anything else first.
+    bool ScreenPtHitsSky(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                       const Point2 &normalized_screen_pt, Point3 *sky_point);
+
+    /// Creates a new sky stroke mesh by projecting each vertex of the 2D mesh
+    /// onto the sky dome and saving the result as a new 3D mesh.
+    void AddSkyStroke(const Matrix4 &view_matrix, const Matrix4 &proj_matrix,
+                      const Mesh &stroke2d_mesh, const Color &stroke_color);
+    
+    /// Draws all of the sky strokes
+    void Draw(const Matrix4 &view_matrix, const Matrix4 &proj_matrix);
+    
+private:
+
+    // Each stroke has a 3D mesh and a color
+    struct SkyStroke {
+        Mesh mesh;
+        Color color;
+    };
+    
+    // To store a new stroke to draw, add it to this array
+    std::vector<SkyStroke> strokes_;
+
+    
+    ShaderProgram *stroke3d_shaderprog_;
+};
+
+#endif